PASS of Xromi Comparing Safety and Effectiveness in Children Under 2 Years With Sickle Cell Disease [PRECISE PASS]

Prospective Exposure Cohort * Inclusion criteria: * Aged from 9 months to under 2 years at the index date. * Diagnosis of SCD. * Known β-globin genotype at the index date. * Prescribed Xromi® for the prevention of complications of SCD. * Parent(s) (or a legal representative(s)) provides written informed consent to participate in the study, unless there is a waiver, non-opposition, or blanket written informed consent by the parent for research studies. * Exclusion criteria: * Previous use of hydroxycarbamide of any formulation before the index date. * Receiving regular blood transfusions (occurring every 8 weeks or more frequently) at the index date. * Known hypersensitivity to any of the excipients of Xromi® at the index date. * Contraindications to the drug at the index date: severe hepatic impairment (Child-Pugh classification C); severe renal impairment (creatinine clearance: CrCl \<30 ml/min); presence of at least one of the following: Absolute neutrophil count (ANC) \< 1.0 x 10\^9/L, absolute reticulocyte count (ARC) \<80 x 10\^9/L, platelets \<80 x 10\^9/L. * Participating in another clinical study of an investigational medicinal product (IMP) at the index date. * Anti-retroviral medicinal products for human immunodeficiency virus (HIV) at the index date. * Active malignancy at the index date. Participants in the prospective exposure cohort who are prescribed Xromi® but do not initiate treatment will be excluded from the dataset. Retrospective Comparator cohort * Inclusion criteria: * Aged from 9 months to under 2 years at the index date. * Diagnosis of SCD. * Known β-globin genotype. * Matched to an exposed participant. * Parent(s) (or a legal representative(s)) provides written informed consent to participate in the study, unless there is a waiver, non-opposition, or blanket written informed consent by the parent for research studies. * Exclusion criteria: * Use of hydroxycarbamide of any formulation before or at the index date. * Receiving regular blood transfusions (occurring every 8 weeks or more frequently) at the index date. * Presence at the index date of any of the following: severe hepatic impairment (Child-Pugh classification C); severe renal impairment (CrCl \<30 ml/min); presence of at least one of the following: ANC \< 1.0 x 10\^9/L, ARC \< 80 x 10\^9/L, platelets \< 80 x 10\^9/L). * Participating in another clinical study of an IMP at the index date. * Anti-retroviral medicinal products for HIV at the index date. * Active malignancy at the index date.